The utilization of solar energy for space heating and cooling has been the subject of various developments for a substantial period of time. Until the recent energy crisis which occured due to scarcity of oil for heating purposes and generation of electric current, practical adaptation of solar energy for heating and cooling, and particularly the actual employment thereof for such purposes, was not seriously undertaken. Now that suitable substitutes for oil and other petroleum products as sources of energy are being considered seriously, the availability of solar energy for such purposes is very apparent. After the initial installation of a system to employ this form of energy, operation of the same is relatively inexpensive, even when supplemental electrical energy is required to augment solar energy to provide a full schedule of operation of the system.
Various types of solar heat collector systems have been developed heretofore and some of these have now been placed in operation. While not directly related to the present invention, except as an example of one type of solar energy collector system, the present applicant has a co-pending application, Ser. No. 657,883, filed Mar. 4, 1976 and entitled Solar Heat Collector, this collector being suitable for use with the thermal storage and heat transfer system and method comprising the present invention. In some thermal storage and heat transfer systems which have been developed heretofore, heat exchange apparatus has been used in which the heat storage medium which is heated by the solar heat collector, and is circulated through the thermal storage system, comprises water. Similarly, the heat transfer medium also comprises water. Depending upon the type and amount of insulation associated with the system and especially the storage tank, water is relatively useful as a heat storage medium but it is possible to improve the usefulness of a thermal energy storage system by utilizing a heat storage medium in the form of a chemical substance or compound capable of changing from liquid to solid state at a predetermined temperature and thereby developing latent heat of fusion at said temperature which is substantially constant. The principle of deriving such latent heat of fusion from various chemical compound and substantces is well known but, thus far, relatively little use of the same in association with thermal storage system has been undertaken. The present invention, however, utilizes this principle to distinct advantage in association with apparatus structure and the method performed by such structure, details of which are set forth hereinafter.